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Date: Sat, 13 Mar 2021 19:13:00 +0000
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To: PHP internals <internals@lists.php.net>
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Subject: [PHP-DEV] Re: Built-in decorator attribute?
From: davidgebler@gmail.com (David Gebler)

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Oops, didn't tag the subject.

On Sat, Mar 13, 2021 at 4:51 PM David Gebler <davidgebler@gmail.com> wrote:

> With the introduction of attributes in PHP 8, this new behaviour is still
> quite sparsely documented. Some of the articles I've seen out there,
> though, liken PHP's attributes to similar constructs in other languages
> including decorators in Python.
>
> Attributes are not the same thing as (Python's concept of) decorators and
> they shouldn't be confused; a decorator is a function which wraps another
> function and is automatically called in place of the wrapped function.
>
> This isn't currently possible in PHP. Using frameworks like Symfony, we
> can start to build things like this:
>
> class UserProfileController {
>     #[LoginRequired]
>     public function editProfile(...) { }
> }
>
> but the logic of enforcing our "require the user to be logged in"
> decorator relies on the surrounding framework controlling the flow of
> execution, reading the attribute and deciding whether to call the decorated
> method editProfile() at all.
>
> What we *can't* do is something like this:
>
> class Foo {
>     private function timer(callable $wrapped)
>     {
>         $start = microtime(true);
>         $wrapped();
>         $end = microtime(true);
>         $total = $end - $start;
>         echo "Executed function in $total second(s)\n";
>     }
>
>      #[timer]
>     public function bar($a, $b) { ... }
>
>     #[timer]
>     public function baz($a, $b) { ... }
> }
>
> What I'm wondering is whether there's a desire / interest for a built-in
> attribute to provide this kind of behaviour modification.
>
> I'm thinking something like
>
> class Foo {
>     private function timer(callable $wrapped) { ... }
>
>     #[Decorator([self::class, 'timer'])]
>     public function bar() {
>         echo "Bar";
>     }
> }
>
> Where this would result in any call to $foo->bar() being equivalent to as
> if the above were defined as:
>
> class Foo {
>     private function timer(callable $wrapped) { ... }
>
>      public function __bar() {
>         echo "Bar";
>      }
>
>     public function bar() {
>         return $this->timer([$this, '__bar']);
>     }
> }
>
> I'm not saying I have the skills to implement this attribute (though I'd
> happily try), I'm not even in a position to propose a draft RFC at this
> stage, just throwing the idea out there to get a feel for what people think
> of the concept?
>
> Regards,
> Dave
>

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